Methods of preparing polymerizable dental compositions with improved taste or aroma, and that prevent oxygen-inhibited layer

ABSTRACT

Described are methods of improving cure of polymerizable dental materials by preventing oxygen inhibition; preferred embodiments relate to methods wherein the dental compositions comprises a polymerizable sealant and the barrier material comprises an essential oil.

REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of U.S. patent application Ser.No. 09/738,080, filed Dec. 15, 2000, and which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

[0002] The invention relates to the field of polymerizable materials,specifically including polymerizable materials used in the practice ofdentistry, such as sealants. According to the invention, a barriermaterial is used to mask flavor of the polymerizable material, and/or toimpart flavor and aroma, and to prevent oxygen from being exposed to thepolymerizable material during polymerization, thereby preventing oxygenfrom inhibiting polymerization of the material.

BACKGROUND

[0003] Polymerizable materials and related procedures are central ideasin dentistry. Polymerizable adhesives are used in orthodontic treatmentsto adhere brackets to tooth enamel. Polymerizable resin-based materialssuch as pit and fissure sealants are bonded to tooth enamel (e.g., avital tooth, while the tooth is in the patient's mouth) to provide acoating that protects the enamel from decay. Adhesives may be used tosecure a tooth filling material at its margins, to enamel and dentin,and reduce or eliminate the penetration of microbial agents across thesemargins. Adhesive materials may also be used to restore teeth in anumber of ways. When a minor restoration or repair is required, e.g., aswhen a tooth is missing an incisal edge, a polymerizable material can bebonded to the surface of the tooth to replace the lost tooth matter.Adhesive materials are also used where a greater amount of oralrehabilitation is required, as in the cementing of inlays, crowns andbridges, and in aesthetic dentistry, where veneers can be cemented on anenamel facing of a tooth to mask a defect or discoloration.

[0004] Pit and fissure sealants are adhesive dental materials used toprevent tooth decay. Pits and fissures are sites on teeth that my bedifficult to clean, with the risk of plaque stagnation and consequentpossible onset of decay (caries). Pit and fissure caries may account forup to 90% of the total caries experience in some child populations(Combe, E C, Burke F J T & Douglas W H, 1999, Dental Biomaterials, p.165 Boston: Kluwer Academic Publishers). Accordingly, the concept ofsealing pits and fissures with resin applied to an etched enamelsurface, known as fissure sealing, was developed in the 1960s, after theintroduction of the acid-etch technique in 1955 (Buonocore M G, 1955,Journal of Dental Research, 34: 849-853). Such treatment is of benefitto patients at risk of occlusal caries, because the sealant will protectthe susceptible pits and fissures from plaque accumulation andsubstrates that may be metabolized into destructive acids.

[0005] Of course, dental procedures benefit from patient comfort andpatient cooperation during treatment. This can be difficult consideringthat many polymerizable materials that must be placed in the mouth, suchas sealants, have a disagreeable taste or odor. There is always a needto improve comfort and cooperation of patients during treatment, forexample by finding new ways of eliminating disagreeable tastes and odorsof such materials. Also, it is necessarily a continuing goal to identifyand use dental materials and procedures that are safe and biocompatible.

[0006] Adhesive materials such as sealants commonly includepolymerizable dental materials that cure or harden by chemicalpolymerization reactions. Another problem with some such polymerizablematerials is that their reactions can be inhibited by oxygen. Oxygen isknown to react with free radicals of free-radically-polymerizable dentalmaterials to give peroxide radicals of low reactivity, and which canunite to an oxygen-containing polymer (Combe E C, in ConciseEncyclopedia of Medical and Dental Materials, Editor: Williams D, p. 10Oxford: Pergamon Press). This inhibits polymerization.

[0007] A result of oxygen inhibition can be the formation of a layer atthe surface of the polymerized dental material that is not fullypolymerized (referred to as an “oxygen-inhibited layer” because oxygenhas inhibited some of the desired polymerization reaction). Theoxygen-inhibited layer, having not been completely reacted, containsunreacted or not-fully-reacted components.

[0008] In dentistry, an incompletely-polymerized surface of a dentalmaterial can have undesirable consequences. For example, the taste ofunpolymerized materials can be objectionable, especially to children.Also, there can be health concerns, including the risk of patientexposure to unreacted chemicals of polymerizable dental materials. Somesuch chemicals can exhibit in-vitro cytotoxicity and allergenicpotential. One chemical often used in dental sealants, bis-DMA(bisphenol A dimethacrylate), is said to react with salivary esterasesto form bisphenol A, which is known to be an estrogen-mimicking agent(Rueggeberg, F A, Dlugokinski M & Ergle J W, 1999, Journal of theAmerican Dental Association, 130: 1751-1757).

[0009] Dental practitioners have attempted to minimize exposure ofpatients to unreacted chemicals from dental sealants. See, e.g.,Rueggeberg, F. A., D.D.S., et al., “Minimizing Patients' Exposure toUncured Components in a Dental Sealant,” JADA, Vol. 130, 1751 (December1999). Rueggeberg et al, for example, found that treatments of cureddental materials with mechanical action and a mild abrasive yielded areduction in uncured resin components.

[0010] There exists a need for methods of reducing dental patients'exposure to unreacted components of dental materials. Also, there isroom for improving patient comfort and cooperation in dental proceduresinvolving polymerizable dental materials.

SUMMARY

[0011] The invention relates to materials and methods involvingpolymerizable dental materials. The materials and methods can reduce oreliminate issues relating to the typically disagreeable taste ofpolymerizable dental materials. This is accomplished by the use of abarrier material preferably having desirable flavor and/or aroma, eachof which can improve patient comfort and cooperation, with the aromaalso having potential psychological benefits. The materials and methodsalso improve polymerization of the dental materials by preventing oxygenfrom inhibiting polymerization at the material surface. Improvedpolymerization provides the further benefits of reducing the amount ofunpolymerized materials remaining in the mouth, which further eliminatesdisagreeable taste and also improves the strength of the polymerizedmaterial surface and simplifies procedures relating to application ofthe material in the mouth.

[0012] According to the invention, a barrier material is used to cover apolymerizable dental material placed in the mouth. Preferably, thebarrier material can comprise an oil such as an essential oil. Preferredpolymerizable dental materials include sealants, e.g., pit and fissuresealants. The barrier material covers up the taste of the polymerizabledental material and optionally provides its own desirable flavor andaroma, all of which add to patient comfort and cooperation during theprocedure. At the same time, the barrier material prevents oxygen fromreaching the polymerizable dental material where the oxygen wouldinhibit polymerization. This reduces the inhibitory effect that theoxygen would have on polymerization of the dental material andultimately reduces the amount of unpolymerized material that will remainat the surface of the dental material, which can in turn reduce apatient's exposure to uncured materials.

[0013] An advantage of the invention is that the barrier material can bedesigned to allow for easy removal of the barrier material by rinsing,particularly if the barrier material contains an oil. Overall, themethod is an improvement over past methods used for removing uncuredpolymerizable components from the mouth, such as by application of airor water from a syringe spray, the use of wet or dry cotton rolls,manual use of pumice with a cotton pellet, or the use of pumice inconjunction with a prophy cup in a dental hand-piece. See generally,Rueggeberg et al.

[0014] The methods can be used to prevent oxygen inhibition of anypolymerizable dental material, but can be specifically useful with oraladhesives and pit and fissure sealant.

[0015] An aspect of the invention relates to a method of applying apolymerizable dental sealant to a tooth. The method includes applying abarrier material to the sealant and polymerizing the sealant. Preferredbarrier materials include an oil, e.g., an essential oil.

[0016] Another aspect of the invention relates to a method of applying apolymerizable dental material to a tooth. The method includes applying abarrier material comprising an essential oil to the polymerizable dentalmaterial, then polymerizing the polymerizable material.

[0017] Yet another aspect of the invention relates to a method ofapplying a polymerizable dental sealant to a tooth. The method includespreparing a tooth surface using an etchant, applying a polymerizabledental sealant to the etched surface, applying a barrier material to anexposed surface of the sealant, and polymerizing the sealant.

[0018] Yet another aspect of the invention relates to a method ofpreventing tooth decay. The method includes applying a polymerizable pitand fissure sealant to the tooth, applying a liquid barrier material tothe sealant, the barrier material comprising an oil, and polymerizingthe sealant.

[0019] Yet a further aspect of the invention relates to a method ofcuring a polymerizable dental material. The method includes reducing theamount of oxygen contacting the polymerizable dental material byproviding a barrier material comprising an essential oil on thepolymerizable dental material.

[0020] Yet a further aspect of the invention relates to a compositioncomprising a polymerizable dental material applied to a tooth, and abarrier material comprising an essential oil disposed on a surface ofthe polymerizable dental material.

DETAILED DESCRIPTION

[0021] Polymerizable dental materials include materials used to repair,replace, protect, or otherwise complement the surface of a tooth. Suchmaterials include, for example, sealants, adhesives, composites,restoratives, and the like, which are well known in the dentistry arts.

[0022] The chemistry of the polymerizable dental material can be anychemistry, but the invention can be especially useful in combinationwith polymerizable dental materials whose cure can be inhibited byexposure to oxygen, especially free-radically polymerizable materials.Examples of such dental materials include materials commonly referred toas “resins,” “resin composites,” and “compomers.”

[0023] Generally speaking, resins and resin composites are materialsthat typically cure or harden by free-radical addition polymerizationactivated by chemicals or more usually by radiation, commonly visiblelight. The term “resin” generally refers to the polymerizable componentof a composition (alone or with other materials) while “resin composite”refers to the resin in combination with a filler material. Thus, resinsand resin composites may contain inert inorganic fillers (silica, bariumglass, zirconia/silica glass are some examples) to modify properties.These types of materials adhere micromechanically to tooth enamel,especially after acid etching, and bond to dentin via application of anacid conditioner followed by a primer and/or adhesive, after which acombination of micromechanical and interdiffusion bonding occurs. Manydifferent types of resins and resin composites are commerciallyavailable, and typically vary in the type, concentration, and propertiesof the filler. Representative examples of commercially available resincomposites include, but are not limited to, Revolution (KerrCorporation, Orange, Calif.); Silux (3M, St Paul, Minn.); HRV Herculite(Kerr Corporation, Orange Calif.); Restorative Z100 (3M, St Paul,Minn.); and Alert (Pentron Inc, Wallingford, Conn.).

[0024] Glass ionomers may optionally be included in a polymerizablecomposition, in combination with a polymerizable resin. Glass ionomers,sometimes referred to as polyalkenoate cements, set and/or harden via anacid-base reaction wherein an acidic polymer or copolymer aqueoussolution reacts with an ion-leachable glass. Glass ionomers are wellknown in the dental arts, and include, for example, poly(acrylic acid)and related copolymers which can react with a fluoroaluminosilicateglass (FAS) to give a product including a core containing unreacted FASsurrounded by the acid-base reaction products. Such materials arecommercially available, for example from Ketac-Cem Radiopaque (EspeAmerica, Inc, Norristown Pa.).

[0025] Polymerizable compositions that include a glass-ionomer aresometimes referred to as “resin-modified glass-ionomers” and can be usedin situations where properties intermediate between those of resins andglass-ionomers are desired. Resin-modified glass-ionomers set and hardenvia a combination of an acid-base reaction and a free-radicalpolymerization reaction, which may be activated chemically and byradiation, e.g., visible light. Resin-modified glass-ionomers arewell-known and commercially available. One representative example of acommercially available resin-modified glass-ionomer composition is GCFuji II LC Improved (GC America Inc, Alsip, Ill.).

[0026] Compomers are another class of polymerizable dental materialsthat can be advantageously used where properties intermediate betweenthose of resins or resin composites and glass-ionomers are desired.Compomers are polyacid-modified resin composites that polymerize via afree-radical polymerization mechanism. Compomers are well-known andcommercially available. One example of a commercially available compomerincludes is Compoglass® (Ivoclar North America Inc, Amherst, N.Y.).

[0027] The specific chemistry of the polymerizable dental material canpreferably be any chemistry whose polymerization would be inhibited byoxygen. Many sealants include a mixture of monomers, usually includingacrylates, e.g., di(meth)acrylates (as used herein, the term“(meth)acrylate” refers to both acrylates and methacrylates). Specificexamples of dimethacrylates used in sealant formulations include Bis-GMA(Bisphenol A glycidyl methacrylate, often referred to as “Bowen'sresin”), Bis-DMA, TEGDMA (triethylene glycol dimethacrylate), and UDMA(urethane dimethacrylate). Inert inorganic filler can be included tomodify the appearance and/or mechanical properties of the sealant. Someproducts claim to contain fluoride-containing components.

[0028] Pit and fissure sealants may be classified according to theirsetting mechanism. According to standard specifications (ANSI/ADASpecification No. 39-1992; ISO 6874:1988; British Standard SpecificationBS 7180:1989) there are two types of materials. Type 1 materials includea chemical setting mechanism, meaning that they contain a chemicalactivator. Type 2 materials are described as “external-energy-cured,”meaning they cure upon application of an external source of energy suchas visible light of an appropriate wavelength and intensity. Type 2materials are often referred to as visible-light cure (VLC) materials.Both types of sealant set (i.e., polymerize) essentially by free-radicaladdition polymerization.

[0029] Examples of commercially available sealants include Concise™White Sealant, available as Type 1 or a Type 2 material (3M Company, St.Paul, Minn.), FluoroShield™ (Type 2, Dentsply/Caulk, Milford, Del.),Helioseal® (Type 2, Ivoclar/Vivadent, Buffalo, N.Y.), Prisma-Shield®(Type 2, Dentsply/Caulk, Milford, Del.), Sealite™ (Type 2, Kerr USA,Romulus, Mich.) and Seal-Rite™ (Type 2, Pulpdent, Watertown, Mass.).

[0030] According to the invention, a barrier material is applied to thepolymerizable dental material prior to polymerization, e.g., after thematerial has been placed in the mouth. The barrier material can cover ormask the taste of the polymerizable dental material. The barriermaterial can also impart its own desirable flavor and aroma into theprocess, allowing for improved patient comfort and cooperation; in thisregard the barrier material can impart the flavor and odor of anessential oil and can optionally and preferably act as a vehicle forincorporating additional flavor or aroma such as by an added flavoring.Moreover, the barrier material can act as a barrier to prevent oxygenfrom contacting the polymerizable dental material, providing improvedpolymerization of the polymerizable material. As noted above,polymerization of polymerizable materials can be inhibited by oxygen.According to the invention, the barrier material is placed on a surfaceof the material to prevent oxygen from contacting the material where theoxygen would inhibit polymerization.

[0031] Because the barrier material is being used in dentistryenvironments, a number of features are important. The barrier materialshould be biocompatible, consisting of materials acceptable for oraluse. When the barrier material is used with a radiation-curable dentalmaterial, the barrier material should be able to transmit suchradiation. This is true, for example, when using the invention with Type2 sealant materials where light must reach the sealant to activatepolymerization. A barrier material should preferably form a continuousfilm over the polymerizable dental material. The barrier material shouldbe chemically compatible with the polymerizable dental material and notcause chemical degradation. This of course will depend on thecomposition of the polymerizable dental material. The barrier materialshould be of a character that will at least cover up or mask a flavor ofthe polymerizable dental material, or ideally have a flavor and aromathat is tasteful. And, the barrier material should be convenient toapply to a tooth in a patient's mount.

[0032] The barrier material can preferably be a liquid comprising orbased on an oil. Preferred oils include essential oils, for examplesoybean oil, safflower oil, sesame oil, olive oil, sunflower oil, canolaoil, walnut oil, peanut oil, orange oil, eucalyptus oil, cod liver oil,castor oil, or a combination of two or more of these oils. Essentialoils are suitable for use as a barrier material because many exhibit oneor more properties including suitable flavor and/or liquidity for easeof application, chemical inertness, film-forming capability, andtransparency to electromagnetic radiation. Also, essential oils areknown to be compatible with resin based filling materials (see generallyApplicants' U.S. patent application Ser. Nos. 09/427,876, 09/427,943,the disclosures of which are incorporated herein by reference).

[0033] An essential oil may be used by itself as the barrier material, amixture of essential oils may be used, or an essential oil may be usedwith other ingredients (e.g., flavoring agents) included in amounts thatdo not unduly hinder the ability of the barrier material to cover aflavor or odor of the polymerizable dental material or to reduce theamount of oxygen reaching the polymerizable dental material.

[0034] Those with an understanding of polymerizable dental materialswill understand that materials other than essential oils, for exampleother types of oils, may also be used in a barrier material, singly orin combination with essential oils or other materials. For example,liquids such as glycerol and propylene glycol can be used in combinationwith an essential oil. A flavor included in a barrier material may beany of a variety of desirable flavors, for example cherry, strawberry,blueberry, watermelon, lemon, lime, raspberry, apple, grape, cranberry,coconut, banana, tangerine, pineapple, bubble gum, almond, hazelnut,chocolate, etc.

[0035] The barrier material is applied to a surface of a polymerizabledental material, preferably by first placing the polymerizable dentalmaterial in the mouth, particularly at a tooth, and then applying thebarrier material. Next, the polymerizable dental material can bepolymerized. The polymerizable dental material is typically applied to atooth after some preparation of the tooth, as is appropriate for thespecific dental procedure and material being used. This can includecleaning and often some application of a primer or other treatment topromote adhesion. The polymerizable dental material is then applied tothe prepared surface, as needed. Following placement of thepolymerizable dental material, the barrier material is applied to theexposed surface of the dental material, and the dental material is thenpolymerized by appropriate means. The barrier material covers or masksthe flavor of the dental material, and also reduces the amount of oxygencontacting the polymerizable dental material, preferably to entirelyprevent environmental oxygen from contacting the dental material. Thebarrier material is applied to the polymerizable dental material in anyfashion that will accomplish this, preferably in a fashion that willresult in a continuous coating (e.g., a film) of barrier material overthe surface of the polymerizable dental material. Examples of methods ofapplying the barrier material to a polymerizable composition includedropping, spreading, spraying, or brushing the barrier material onto thepolymerizable dental material

[0036] Specifically with respect to sealants, application of a sealantinvolves preparation of the tooth by first cleaning and drying a toothsurface. An etchant, usually based on phosphoric acid, is applied to thesurface, e.g., a fissure, for typically 15 seconds, and the surface iswashed to remove etching debris and thoroughly dried. The sealant isapplied to the etched surface. According to the invention, a barriermaterial is applied to the exposed surface of the sealant, preferably inan amount and manner to form a continuous film over the sealant. Thesealant is then polymerized. Optionally the barrier material can bewashed away by rinsing with water.

EXAMPLE

[0037] A Type 2 fissure sealant (Helisoseal®, Ivoclar/Vivadent, Buffalo,N.Y.) was used in this study, tested by the method of Section 6.6 ofANSI/ADA Specification No. 39-1992). A drop of the sealant was placed ona microscope slide and covered with a glass cover slip to give anapproximately round mass of sealant, with an edge of the materialexposed to air and the two flat surfaces covered by glass.Polymerization was activated using a dental VLC unit (Caulk “The Max”Model 106, Caulk/Dentsply, Milford Del.) with output 470-480 nmwavelength and minimum intensity of 450 mW/square centimeter. The lightwas applied for 10 seconds. On examining the disc of material, visually,using a microscope, an oxygen inhibited zone was detected.

[0038] The above experiment was repeated, except that olive oil wasplaced on the drop of material before the application of the cover slip.When the cover slip was applied, the oil flowed and formed a barrier toair at the circumference of the material. Following polymerization asabove, no oxygen inhibited zone could be detected microscopically.

1. A method of applying a polymerizable dental sealant to a tooth, themethod including applying a barrier material to the sealant andpolymerizing the sealant.
 2. The method of claim 1 wherein the barriermaterial masks a flavor of the polymerizable dental material.
 3. Themethod of claim 1 wherein the barrier material provides an oxygenbarrier to prevent oxygen from contacting the polymerizable dentalmaterial, to prevent the oxygen from inhibiting polymerization of thepolymerizable dental material.
 4. The method of claim 1 wherein thebarrier material comprises an oil.
 5. The method of claim 1 wherein thebarrier material comprises an essential oil.
 6. The method of claim 5wherein the essential oil is chosen from the group consisting of soybeanoil, safflower oil, sesame oil, olive oil, sunflower oil, canola oil,walnut oil, peanut oil, orange oil, eucalyptus oil, cod liver oil,castor oil, and a combination of two or more of these oils.
 7. Themethod of claim 1 wherein the barrier material comprises a flavoring. 8.The method of claim 1 wherein the polymerizable dental material isfree-radically polymerizable.
 9. The method of claim 1 wherein thepolymerizable dental sealant comprises a resin, a resin composite, acompomer, or a mixture thereof.
 10. The method of claim 1 wherein themethod comprises applying a liquid barrier material to the sealant bydropping, spreading, spraying, or brushing the liquid barrier materialonto the sealant.
 11. A method of applying a polymerizable dentalmaterial to a tooth, the method including applying a barrier materialcomprising an essential oil to the polymerizable dental material, thenpolymerizing the polymerizable material.
 12. The method of claim 11wherein the barrier material masks a flavor of the polymerizable dentalmaterial.
 13. The method of claim 11 wherein the barrier materialprovides an oxygen barrier to prevent oxygen from contacting thepolymerizable dental material, to prevent the oxygen from inhibitingpolymerization of the polymerizable dental material.
 14. The method ofclaim 11 wherein the essential oil is chosen from the group consistingof soybean oil, safflower oil, sesame oil, olive oil, sunflower oil,canola oil, walnut oil, peanut oil, orange oil, eucalyptus oil, codliver oil, castor oil, and a combination of two or more of these oils.15. The method of claim 11 wherein the barrier material furthercomprises a flavoring.
 16. The method of claim 11 wherein thepolymerizable dental material is free-radically polymerizable.
 17. Themethod of claim 11 wherein the polymerizable dental material comprises aresin, a resin composite, a compomer, a glass ionomer, or a mixturethereof.
 18. The method of claim 11 wherein the method comprisesapplying a liquid barrier material to the polymerizable dental materialby dropping, spreading, spraying, or brushing the liquid barriermaterial onto the polymerizable dental material.
 19. A method ofapplying a polymerizable dental sealant to a tooth, the methodcomprising preparing a tooth surface using an etchant, applying apolymerizable dental sealant to the etched surface, applying a barriermaterial to an exposed surface of the sealant, and polymerizing thesealant.
 20. The method of claim 19 wherein the sealant is applied to afissure.
 21. A method of preventing tooth decay by the applying to atooth a pit and fissure sealant, the method comprising applying apolymerizable pit and fissure sealant to the tooth, applying a liquidbarrier material to the sealant, the barrier material comprising an oil,polymerizing the sealant.
 22. The method of claim 21 further comprisingrinsing the barrier material from the tooth.
 23. The method of claim 21wherein the oil comprises an essential oil.
 24. A method of curing apolymerizable dental material, the method comprising reducing the amountof oxygen contacting the polymerizable dental material by providing abarrier material comprising an essential oil on the polymerizable dentalmaterial.
 25. The method of claim 24 wherein polymerization of thepolymerizable dental material is inhibited by oxygen.
 26. The method ofclaim 24 wherein the method prevents the formation of anoxygen-inhibited layer in the polymerizable dental material.
 27. Themethod of claim 24 wherein the barrier material consists essentially ofan essential oil or a mixture of essential oils, optionally, incombination with a flavoring.
 28. A composition comprising apolymerizable dental material applied to a tooth, and an oxygen barriermaterial comprising an essential oil disposed on a surface of thepolymerizable dental material.
 29. The composition of claim 28 whereinthe polymerizable dental material is a sealant.